In the UMTS (Universal Mobile Telecommunications System) network, the specifications of long term evolution (LTE) have been drafted for the purpose of further increasing high speed data rates, providing lower delays and so on (see non-patent literature 1). In LTE, as multiple-access schemes, a scheme that is based on OFDMA (Orthogonal Frequency Division Multiple Access) is used in downlink channels (downlink), and a scheme that is based on SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in uplink channels (uplink).
Furthermore, successor systems of LTE (referred to as, for example, “LTE-advanced” or “LTE enhancement” (hereinafter referred to as “LTE-A”)) have been under study for the purpose of achieving further broadbandization and increased speed beyond LTE. In the LTE-A system, a HetNet (Heterogeneous Network), in which small cells (for example, pico cells, femto cells and so on), each having a local coverage area of a radius of approximately several tens of meters, are formed inside a macro cell having a wide coverage area of a radius of approximately several kilometers, is under study (see, for example, non-patent literature 2). Also, in relationship to the HetNet, a study is in progress to use carriers of different frequency bands between a macro cell (macro base station) and a small cell (small base station), in addition to the same frequency band.